A variety of inexpensive mechanical toy aquatic creatures, such as fish and sharks, can be found in typical toy stores. The selling point of many of these toys arises from their ability to propel themselves through a fluid medium such as water. Small motors positioned within the creatures are operatively connected to mechanisms which oscillate their respective tails to make the creatures swim. However, despite the best efforts of toy manufacturers, these creatures swim in a manner which will almost assuredly not be confused with actual fish. The mechanical construction of the toys produces an equally mechanical swimming operation, a motion not found in smoothly flexible living fish. Moreover, the need for a battery power source, as well as the multiple piece drive mechanism, results in high manufacturing and assembly costs.
Several representative mechanical constructions are well known in the art. For instance, in providing propelling means, some toy designs utilize a rigid tail fin which simply pivots relative to the fish body in constant back and forth manner. This type of motion is most similar to ostraciiform motion exhibited by some species of fish. While the pivoting of the rigid tail fin does serve to propel the toy, it appears substantially different from the tail motion normally attributed to typical swimming fish, and therefore appears non-lifelike. Other designs, as disclosed in U.S. Pat. Nos. 3,785,084, 4,713,037 and 4,832,650 strive to better imitate the curvy fish tail movement associated with carangiform motion. This motion, which is more familiar to the public as it is a motion characteristic of fish such as salmon or trout, is attempted to be imitated by employing an articulated, two-piece tail section made up of rigid segments. The forward piece of the tail section is mechanically oscillated, while the rearward piece of the tail section is freely pivotable thereon. Nonetheless, despite being more recognizable as a fishlike swimming motion than a pivoting one-piece tail design, the two-piece tail design still falls woefully short of properly imitating the smooth swimming motions of a live fish.
Another shortcoming of aquatic creature toys relates to the limited span of time in which users, normally children, find them interesting. While almost all toys eventually lose their novelty, the fact that the current aquatic toys do not require hands-on participation accelerates the process. The excitement of play first provided by these toys gradually turns to boredom because users perform such a passive role. After activating these toys and placing them in, for instance, a bathtub, the only thing left for a user to do is idly watch.
Focused efforts to develop devices which imitate the swimming motion of fish in a lifelike manner are not limited to the toy manufacturing industry. The scientific community has long been interested in understanding how fish swim, as evidenced by Breeder, Charles M. Jr., "The Locomotion of Fishes" Zoologica, Vol. IV, No. 5 (1926), which is herein incorporated by reference. Members of the scientific community, in their efforts to achieve a better understanding of fish motion, have also created devices used to explain or recreate the swimming motion of fish. For instance, scientific devices or models with various mechanical attachments which attempt to imitate the swimming undulating motion of fish are disclosed in Animal Locomotion by Sir James Gray, published in 1968 by Weidenfeld and Nicolson, and Fish Biomechanics edited by Paul Webb and Daniel Weihs, published in 1983 by Praeger, which are herein incorporated by reference.
The motivation of the scientific community for developing a swimming fish simulator are many in number. For example, providing a simulator which a researcher can precisely operate and command allows a more exact control to be utilized in fish studies or research; where tail beat frequency and amplitude can be continuously and precisely controlled by the operator the relationships among these parameters and the speed of swimming can be analyzed. Another important reason for developing simulators is to gain a better understanding of the propulsion mechanics of various types of aquatic creatures. Different species of fish have different body shapes and amounts of fast (white) and slow but long-enduring (red) muscle. Some are sprinters, some are cruisers, and some are highly maneuverable. By varying shape parameters and the pattern of actuation of simulators, scientists can learn which combinations of shape, stiffness, and actuation patterns provide the highest locomoter performance of fishes and other aquatic animals. Engineers can use this information to design driven and autonomous underwater vehicles of increased efficiency. By learning about fish and putting gained knowledge into practice in simulators, scientists can begin tapping the energy efficiencies in the swimming motion of fish which nature has perfected over several hundred million years.